How to access Azure VM from App Service in virtual network by private DNS name? - azure

VM and App Service are located in the same Virtual Network.
App Service is added to VM through VNet Integration (preview)
VM is autoregistered in Private DNS zone, say by name myvm1. And full name myvm1.priv.zone
Private DNS zone is linked to Virtual Network.
Virtual Network - DNS Servers is set to default.
VM and App Service were restarted after configuration.
Problem is I can resolve neither myvm1 nor myvm1.priv.zone from App Service console by nameresolver.exe
UPDATE:
Actually, the issue is even bigger. App Service is not able to send requests to VMs in Virtual Network by their Private IPs (10.1.x.x) even if everything is allowed on VMs' subnet. If the same requests are sent to VMs' Public IPs there is no problem.

As the existing answer, for scenario Name resolution from App Service Web Apps to VMs in the same virtual network. in this DOC, you need to deploy your own DNS server to help name resolution.
Here are the steps:
On the Azure VM in the VNet, add a server role DNS server, after the installation, configure the DNS server, add Zone name such as qaz.lab in my example. You also can manually add an A record for your Azure VM in this Zone.
Add the DNS server private IP address in the custom DNS server of Azure VNet. Then restart the Azure VM to make it effective.
Configure VNet Integration with your app, in this case, select the new VNet integration. After that, refresh your VNet Integration. You will see the DNS server update in your app service plan --- networking.
Navigate your app service, run nameresolver FQDN to validate the DNS resolution. Currently, It only supports FQDN resolution.
Let me know if you have any question.

As of today, you need to use DNS proxies or forwarders to achieve your ask. It is documented here in the scenario table.
For scenario "Name resolution from App Service Web Apps to VMs in the same virtual network.", the solution is to "Customer-managed DNS servers forwarding queries between virtual networks for resolution by Azure (DNS proxy)."
On How to perform "Name resolution with your own DNS" check here, where your scenario is described.

Related

Azure Virtual Machine cannot resolve DNS entry of Application Gateway

I have the following situation:
If I deploy an application (Deployment, Service and Ingress) in my kubernetes cluster, my ingress deployment is being automatically added to my application gateway (I am using the Azure Application Gateway Ingress Controller; https://azure.github.io/application-gateway-kubernetes-ingress/annotations/ ). So far so good.
That means that my application can be reached via my application gateway via https://my-app-gateway-public-ip/myAppPath/. Also, I have an additional private DNS zone which makes my app accessible via https://dns-name/myAppPath.
Additionally, we have an AADDS in combination with a Bastion Service. Deployed some virtual machines and the virtual machines use the DNS resolver of the AADDS (for authentication against the AAD).
The problem is: If I am outside of the cloud, I can nslookup the dns or can access the site via the ip, but I cannot do that with my virtual machines. My DNS server (within the AADDS) is unable to resolve the dns or accessing the ip. I am wondering what the issue is.
The bastion and AADDS are in different subscriptions and therefore different virtual networks. I established already a peering between those virtual networks (or the authentication between the AADDS and the VMs wouldn't work).
The kubernetes cluster and the application gateway are also in a different subscription, but no peering has been done so far.
Are there any hints what I could be missing?
Kind regards
• Since, you are using a Bastion gateway server to connect to the VMs hosted in your subscription, the Bastion gateway server must be having a public IP address through which then the registered underlying VMs can be connected to via private links created in the private DNS zones associated with a particular virtual network in a subnet and an assigned private IP address and a FQDN accordingly. Thus, if you want to access the application website hosted behind the application gateway, then you will have to create a conditional forwarder in the DNS zone in AADDS to redirect the internal requests from the VMs hosted within a virtual network to the public IP address of the website hosted behind the application gateway
• Thus, a conditional forwarder forwards the DNS resolution requests for a particular resource hosted on the public internet for which the DNS host resolution is not found or done in that DNS zone which usually serves or fulfils the requests related to internal environment. As a result, when a VM configured with a private IP is registered as a host in the internal DNS zone queries the public IP or FQDN associated with the application’s website, the DNS requests are forwarded to the public internet through the conditional forwarder and then the results are displayed in the VM’s browser for the application’s webpage. Thus, the VMs don’t need to have internet access but the DNS server should have or should forward the requests through the Internet proxy server accordingly to reach the internet.
For more information on creating conditional forwarder in AADDS, kindly refer to the below link: -
https://learn.microsoft.com/en-us/azure/active-directory-domain-services/manage-dns#create-conditional-forwarders

AZURE vm, not confugured

can anyone help with some azure vm issues. I wished to connect a domain server VM and a ordinary server VM and use active directory synchronization. But every time I deploy new VM from azure portal, it always have the DNS name status as not configured. I really don't understand why. I set the DNS server with the private IPs of the VMs on the vNet. Thanks for replies and advise. VM DNS name not configured
As the comment stated, the DNS name for that VM is actually associated with the public IP attached to that VM. You can follow this step to create FQDN for an Azure VM.
If you want to join the Azure VM to your local domain, you can follow this link:
The main steps are as follows:
Establish cross-site connectivity using Azure site-to-site VPN connections
Configure a custom DNS server
Provision a VM with a custom DNS server
Join the Azure VM to the on-premises Active Directory domain
If you intend to join a Windows Server virtual machine to an Azure Active Directory Domain Services managed domain, read this tutorial.

Cannot access Private AKS cluster from Local Machine (on home network) connected to Azure VPN

I have a Private AKS cluster deployed in a VNET on Azure. Once I deployed it, a private endpoint and a private DNS zone were created by default therefore making the cluster accessible from VM's which are part of the same VNET. (I have a VM deployed in the same VNET as the AKS cluster and "kubectl" commands work in it.)
My requirement is that I want to perform the "kubectl" commands from my local machine (connected to my home network) and also connected to the VPN which connects to the VNET.
My machine can talk to resources within the VNET but cannot seem to resolve the FQDN of the private cluster.
I read somewhere that having a DNS forwarder setup in the same VNET can help resolve the DNS queries made from the local machine which can then be resolved by Azure DNS. Is this the way to go about this? Or is there a better way to solve this problem?
It would really help if someone could give me an action plan to follow to solve this problem.
The better way to perform the "kubectl" commands from your local machine to your private AKS cluster is to use AKS Run Command (Preview). This feature allows you to remotely invoke commands in an AKS cluster through the AKS API. This feature provides an API that allows you to, for example, execute just-in-time commands from a remote laptop for a private cluster. Before using it, you need to enable the RunCommandPreview feature flag on your subscription and install aks-preview extension locally. However, there is a limitation that AKS-RunCommand does not work on clusters with AKS managed AAD and Private link enabled.
In this case, If you want to resolve the FQDN of the private cluster from your on-premise network, you could select to use either the hosts file locally(used for testing) or use your DNS forwarder to override the DNS resolution for a private link resource like this.
The DNS forwarder will be responsible for all the DNS queries via a server-level forwarder to the Azure-provided DNS 168.63.129.16.You can provision IaaS Windows VM with DNS role or Linux VM with bind configured as a DNS forwarder. This template shows how to create a DNS server that forwards queries to Azure's internal DNS servers for Linux VM. Refer to this for DNS forwarder on Windows VM.
If there is an internal DNS server in your on-premise network. The on-premises DNS solution needs to forward DNS traffic to Azure DNS via a conditional forwarder for your public DNS zones(e.g. {region}.azmk8s.io). The conditional forwarder references the DNS forwarder deployed in Azure. You could read this blog about DNS configuration sections for more details.

Is it possible to create the equivalent of a hosts file in an azure web app

I'm migrating asp.net services that used to exist on a physical server on-premise to Azure. However they need to reach some web-services (SOAP) that will not be migrated to azure yet. These have a public IP but I need to set the hostname in order for IIS to properly redirect the requests to the correct service as there are several on the same server. Is there any way to create some sort of DNS-server in azure that is only available for the services created in azure that can resolve to the public IP-address outside of azure? (We have used the hosts file on the servers to achieve this previously)
I tried using the private DNS Zones, but as I've understood it they can only point to other azure services within the same vnet (correct me if I'm wrong). I've also tried creating a dnsmasq docker container. However, as this is running in a Linux container, it seems that I cannot put it in the same vnet as the asp.net app services. Thus I am unable to retrieve a private IP-address that these services can use to reach the DNS server.
In my understanding it is now possible to use Azure DNS Private Zones if you want.
You would need to use regional vnet integration to point your app's traffic to a vnet that is connected to the Private Zone. You need the following settings as well, which mean that all outbound traffic from the Web App is routed through the integrated vnet first, and that the Azure default DNS server is used for DNS.
WEBSITE_DNS_SERVER with value 168.63.129.16
WEBSITE_VNET_ROUTE_ALL with value 1
https://learn.microsoft.com/en-us/azure/app-service/web-sites-integrate-with-vnet#azure-dns-private-zones
If you don't want to use Azure DNS Private Zones, I think you can achieve similar results by directing the Web App to use a specific DNS server. This can be done using WEBSITE_DNS_SERVER and WEBSITE_DNS_ALT_SERVER app settings (the values are the IP addresses of the servers you want to use).
This is the most authoritative public statement I can find about using these settings.
Go to the web app->settings->Application Settings-> App Settings
section
Add the following: (WEBSITE_NODE_DEFAULT) should already be
there.
a. WEBSITE_DNS_SERVER with value having the IP address of the
primary DNS server.
b. WEBSITE_ALT_DNS_SERVER (optional), with value
having the IP address of a second DNS server.
Then save the settings & restart webapp in portal.
Double check the web app can actually
connect to the DNS server: a. In kudu console, run: Nameresolver.exe
[hostname-to-lookup] [dns-server-to-use]
First argument should be the
hostname you are trying to look up, second argument is one of the DNS
servers from step 1) If this times out, there is an issue with how
your DNS servers are configured (firewalls, etc.)
https://github.com/MicrosoftDocs/azure-docs/issues/13927#issuecomment-416382230
If using these settings with a DNS server that is only accessible via private IP, you would need to use regional vnet integration again to connect to a vnet. If the DNS server is on-prem, you have to connect through the integrated vnet over VPN or ExpressRoute.
It's possible but not using the private DNS Zone.
According to Name resolution for resources in Azure virtual networks. For the scenario Name resolution from App Service Web Apps in one virtual network to VMs in a different virtual network, you need to use your own DNS servers forwarding queries between virtual networks for resolution by Azure (DNS proxy). See Name resolution using your own DNS server.
In this case, you only allow this azure web service could resolve the public IP address outside of Azure. You could enable virtual network integration for your web app, this restricts your web app access in a private network. Then you could deploy a DNS server in the same Vnet as the web app integrated VNet. You could create an A type record in your DNS zone to point to your service Public IP, then add the DNS server's IP address into the DNS server of the Integrated web app Vnet in the portal. If so, the web app could resolve this public IP via a custom DNS server.
Hope this could help you.

Azure DNS zone record not resolving to specified IP from App service to Virtual Machine

I followed the documentation guide here to configure an Azure DNS zone for a virtual network.
I then created a virtual machine on that virtual network and provisioned a virtual network gateway to allow my Azure web apps to communicate with the virtual machine using VNet integration. My web apps are then able to resolve against the virtual machines private IP as expected.
I then created an 'A' type record set within the DNS zone resolving a service name against the private IP of the virtual machine just like here.
However, when I then attempt to access the DNS configured service name that should resolve against the private IP address of the virtual machine, I get the following error:
curl: (6) Could not resolve host: xxxx.local
Am I missing something obvious here?
I can not reproduce this error following your steps:
Create an Azure VNet with a DNS private zone like private.test.com.
Create a VM and a VPN gateway on that VNet.
Enable VNet integration with my Azure web app service.
My web apps are able to resolve against the virtual machines private IP as expected. This could verify the Azure private DNS zone should work. Then I also create an A record for a custom name against the VM private IP address. Both scenarios work.
You could check if an A record is something like below picture in the private DNS zone.
Then you could verify if curl with http:// or without that, or without the specific port 9200, the error is still the same.
I suggest using SET WEBSITE_DNS_ command. This command will output the current DNS server that is being used by the web app. If the error Environment variable WEBSITE_DNS_ not defined is received, no custom DNS servers are configured for the web app. See more details about networking Related Commands for Azure App Services.

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